(Reuters) - Republican presidential candidate Marco Rubio, 44, frequently plugs his youth on the campaign trail but his promise to restore the American Dream for a new generation seems to appeal more to older age groups.

As the U.S. senator from Florida rises in opinion polls of Republicans, his gains are coming from voters over the age of 50, and most from those older than 65, according to Reuters/Ipsos polling.

Although Rubio is running third overall behind Donald Trump and Ben Carson, he is tied with Carson with 12 percent among those older than 65, up from only 7 percent in late October.

Yet his support in the online survey is flat among voters his own age and younger. He registers at just six to seven percent among Republicans younger than 49.

In interviews with two dozen of the poll respondents over 50, 14 preferred Rubio after watching Republican debates this fall because they believed he was best able to stand up to his opponents while projecting a positive tone rather than acidity.

Two-thirds of those interviewed also mentioned being attracted to the Cuban-American senator's personal history, which he has worked into key moments in each debate as Republicans fight to win their party's nomination for the November 2016 election.

“Rubio’s initial bump in the polls is due to older voters really liking his story,” said Monmouth University pollster Patrick Murray, whose surveys also found increases for Rubio among older voters in early voting states like New Hampshire and South Carolina.

Evoking the American Dream, Rubio often talks about his parents who fled Cuba for the United States where they worked as a bartender and maid. He talks about being raised from paycheck to paycheck and working to put himself through college.

Sixteen of the 24 older voters Reuters spoke to this week also cited Rubio's relative youth compared with many of the other leading candidates as a positive attribute.

Rose Jegierski, 67, from Albany, New York, was among them. “He’s got more pep and vinegar than an older man.”

Four of those voters even compared Rubio to John F. Kennedy, a Democrat elected president in 1960 aged 43.

“I think he would be like Kennedy,” said Rhoda Pelliccia, a 76-year-old Republican New Yorker living in Florida. “Kennedy was young and look what he did.”

RELIABLE OLDER VOTERS

Rubio’s advisers say they are not surprised or worried by the disparity and point out that older Americans are a crucial group because they reliably go to the polls.

While pollsters say he must broaden his appeal and attract younger voters to secure the nomination, Rubio’s aides say the candidate has no plans to change his message and they believe younger voters eventually will come his way.

“Our message is entirely about the future, but a part of that is creating an America where parents can pass on a better country than the one they inherited,” Rubio’s chief strategist, Todd Harris, said. “Older voters understand that because they’ve lived it and it’s what their parents did for them.”

Some elements of Rubio's agenda seem targeted to younger voters like those with children. He is proposing to allow approved investors to help students finance a post-secondary education. Himself a father of four, he wants an expanded child tax credit that would jump to $2,500 per child under 16 from $1,000 today.

But several younger voters said they were less familiar with Rubio than with Trump and that they preferred the real estate mogul because he would represent more of a change from the status quo in Washington.

LeighAnn Mangum, a 33-year-old accountant from Mississippi, said she had a positive impression of Rubio but felt Trump stood out as having a strong performance on the debate stage. "He is something new," Mangum said of Trump.

Rival campaigns chastise Rubio for personal financial mistakes such as facing foreclosure on a home and cashing out some retirement savings.

But Monmouth's Murray said that Rubio's financial struggles are part of why older people relate to him. Minnesota voter Roger Olson, 64, said he thinks 99 percent of the country has gone through similar trouble.

Rubio says he still owed $100,000 in student loans just four years ago, a message aimed at showing he understands challenges facing young people and middle-class families.

All the same, Rubio is taking great care to address entitlement programs and the concerns of senior citizens, who often make up the bulk of audiences at his campaign events.

“I’m from Florida. You may not know this, but there are a lot of people in Florida on Medicare and Social Security,” he says, barely pausing for his crowds to laugh, as they realize how many older voters retire in the southern state. “One of them happens to be my mother. And I can say this to you right now unequivocally: I am against anything that is bad for my mother,” he said in Bedford, New Hampshire last month.

Rubio vows not to change those programs for the already retired or for those nearing retirement age. But he acknowledges that they must change for future generations.